Plants' oil-production accelerator also activates the brakes

Scientists discover seemingly paradoxical mechanism for regulating oil synthesis

Date: June 20, 2019 Source: DOE/Brookhaven National Laboratory 

Summary:

Scientists studying plant biochemistry recently made a surprising discovery: They found that a protein that turns on oil synthesis also activates a protein that puts the brakes on the same process. They describe how this seemingly paradoxical system keeps oil precursors perfectly balanced to meet plants' needs.

See more at:

https://www.sciencedaily.com/releases/2019/06/190620104903.htm

What flowers looked like 100 million years ago

Date: August 2, 2017 Source: University of Vienna Summary: Flowering plants with at least 300,000 species are by far the most diverse group of plants on Earth. They include almost all the species used by people for food, medicine, and many other purposes. However, flowering plants arose only about 140 million years ago, quite late in the evolution of plants, toward the end of the age of the dinosaurs, but since then have diversified spectacularly. No one knows exactly how this happened, and the origin and early evolution of flowering plants and especially their flowers still remains one of the biggest enigmas in biology, almost 140 years after Charles Darwin called their rapid rise in the Cretaceous "an abominable mystery".

Flowering plants with at least 300,000 species are by far the most diverse group of plants on Earth. They include almost all the species used by people for food, medicine, and many other purposes. However, flowering plants arose only about 140 million years ago, quite late in the evolution of plants, toward the end of the age of the dinosaurs, but since then have diversified spectacularly. No one knows exactly how this happened, and the origin and early evolution of flowering plants and especially their flowers still remains one of the biggest enigmas in biology, almost 140 years after Charles Darwin called their rapid rise in the Cretaceous "an abominable mystery."

This new study, the "eFLOWER project," is an unprecedented international effort to combine information on the structure of flowers with the latest information on the evolutionary tree of flowering plants based on DNA. The results shed new light on the early evolution of flowers as well as major patterns in floral evolution across all living flowering plants.

Among the most surprising results is a new model of the original ancestral flower that does not match any of the ideas proposed previously. "When we finally got the full results, I was quite startled until I realized that they actually made good sense," said Hervé Sauquet, the leader of the study and an Associate Professor at Université Paris-Sud in France. "No one has really been thinking about the early evolution of flowers in this way, yet so much is easily explained by the new scenario that emerges from our models."

According to the new study, the ancestral flower was bisexual, with both female (carpels) and male (stamens) parts, and with multiple whorls (concentric cycles) of petal-like organs, in sets of threes. About 20% of flowers today have such "trimerous" whorls, but typically fewer: lilies have two, magnolias have three. "These results call into question much of what has been thought and taught previously about floral evolution!," said Juerg Schoenenberger, a Professor at the University of Vienna, who coordinated the study together with Hervé Sauquet. It has long been assumed that the ancestral flower had all organs arranged in a spiral.

The researchers also reconstructed what flowers looked like at all the key divergences in the flowering plant evolutionary tree, including the early evolution of monocots (e.g., orchids, lilies, and grasses) and eudicots (e.g., poppies, roses, and sunflowers), the two largest groups of flowering plants. "The results are really exciting!" said Maria von Balthazar, a Senior Scientist and specialist of floral morphology and development at the University of Vienna. "This is the first time that we have a clear vision for the early evolution of flowers across all angiosperms."

The new study sheds new light on the earliest phases in the evolution of flowers and offers for the first time a simple, plausible scenario to explain the spectacular diversity of floral forms. Nevertheless, many questions remain. The fossil record of flowering plants is still very incomplete, and scientists have not yet found fossil flowers as old as the group itself. "This study is a very important step toward developing a new and increasingly sophisticated understanding of the major patterns in the evolution of flowers," said Peter Crane, President of the Oak Spring Garden Foundation and a colleague familiar with the results of the study. "It reflects great progress and the results on the earliest flowers are especially intriguing."

Story Source:

Materials provided by University of Vienna. Note: Content may be edited for style and length.

Journal Reference:

Hervé Sauquet, Maria von Balthazar, Susana Magallón, James A. Doyle, Peter K. Endress, Emily J. Bailes, Erica Barroso de Morais, Kester Bull-Hereñu, Laetitia Carrive, Marion Chartier, Guillaume Chomicki, Mario Coiro, Raphaël Cornette, Juliana H. L. El Ottra, Cyril Epicoco, Charles S. P. Foster, Florian Jabbour, Agathe Haevermans, Thomas Haevermans, Rebeca Hernández, Stefan A. Little, Stefan Löfstrand, Javier A. Luna, Julien Massoni, Sophie Nadot, Susanne Pamperl, Charlotte Prieu, Elisabeth Reyes, Patrícia dos Santos, Kristel M. Schoonderwoerd, Susanne Sontag, Anaëlle Soulebeau, Yannick Staedler, Georg F. Tschan, Amy Wing-Sze Leung, Jürg Schönenberger. The ancestral flower of angiosperms and its early diversification. Nature Communications, 2017; 8: 16047 DOI: 10.1038/NCOMMS16047

Cite This Page:

MLA

APA

Chicago

University of Vienna. "What flowers looked like 100 million years ago." ScienceDaily. ScienceDaily, 2 August 2017. <www.sciencedaily.com/releases/2017/08/170802092836.htm>.

How plants decide between growth or defense

Date: August 27, 2019 Source: Leibniz Institute of Plant Genetics and Crop Plant Research Summary: During their daily quest for survival, plants need to strike a careful balance between growth and defence. Both functions are vital for their successful reproduction, however, most plants are not able to do both at the same time. The mechanisms behind this peculiar trade-off are little understood and it has often been hypothesised that restricted energy availability is the main limiting cause.

Grow or defend yourself -- a decision plants need to make on a daily basis, due to their inability to do both simultaneously. For a long time, it was thought that the reason for the growth-defence trade-off might be a question of energy resources. When a plant is defending itself against pathogens, energy could simply be limited for the plant to be growing at the same time, and vice versa. A recent paper published in Cell Reports shines a new light on the poorly understood mechanisms of the trade-off, clarifying that the actual underlying reasons is the incompatibility of the molecular pathways regulating plant growth and defence.

In addition to the observed trade-off, growth and defence need seemingly contradicting requirements. Growth is a process which often necessitates the loosening of the cell wall so that the cells have space to expand. Defence, in many cases calls for a tightening of the cell wall. In this way, the cells form a more solid barricade which is harder to penetrate for pathogens. Within their paper the researchers show that the growth-related transcriptional regulator HBl1 (Homolog of Bee2 Interacting with lBH 1) controls both processes within plants.

By differentially leveraging the expression of NADPH oxidases (NOXs) and peroxidases (POXs), HBl1 regulates ROS homeostasis within the apoplast (the space in between the cell walls of the plant). When plants need to grow, HBI1 is active and configures apoplastic ROS levels that support growth by activating specific NOX genes and repressing specific POX genes. In case of pathogen attack, HBI1 needs to be deactivated, resulting in increased apoplastic ROS levels through the activation of a NOX gene and several POX genes that represses growth but increase disease resistance within the plant.

Due to the contrasting nature of the two processes -- both being regulated by the same transcription factor whilst requiring conflicting ROS levels -- the researchers showed that the growth-defence trade-off is caused by the incompatibility of the pathways, and not by limited energy resources.

The project, which had started four years ago as a Bachelor thesis, was carried out in Aachen. Due to a recent move of the group supervisor, Dr. Schippers, to the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) in Gatersleben, the project was partially evaluated and written up at the Gaterslebener Institute. Dr. Schippers let us know: "With our current findings, we are starting to understand one of the mechanisms behind the growth-defence trade-off. This understanding is crucial if we want to improve plant biomass production without risking impairment of their ability to defend against pathogens."

Dr. Schippers' "Seed Development" research group at the IPK will continue to investigate the different pathways within plant seeds. Dr. Schippers: "As it stands, there are more than 70 peroxidases and 10 NADPH oxidases within plants and we don't exactly know what they are doing. They are of particular interest to me, as peroxidases and oxidases have similar effects within plants and animals. This indicates that their functional conservation predates that of hormones, as hormone signalling pathways evolved specific pathways in plants and humans. We aim to fully untangle these pathways at the cellular level -- so that one day, we can reveal their regulation and function during the development of plants."

Story Source:

Materials provided by Leibniz Institute of Plant Genetics and Crop Plant Research. Note: Content may be edited for style and length.

Journal Reference:

Jakob Neuser, Caroline C. Metzen, Bernd H. Dreyer, Claudio Feulner, Joost T. van Dongen, Romy R. Schmidt, Jos H.M. Schippers. HBI1 Mediates the Trade-off between Growth and Immunity through Its Impact on Apoplastic ROS Homeostasis. Cell Reports, 2019; 28 (7): 1670 DOI: 10.1016/j.celrep.2019.07.029

Cite This Page:

MLA

APA

Chicago

Leibniz Institute of Plant Genetics and Crop Plant Research. "How plants decide between growth or defense." ScienceDaily. ScienceDaily, 27 August 2019. <www.sciencedaily.com/releases/2019/08/190827123543.htm>.

New mutations for herbicide resistance rarer than expected

Date: May 28, 2019 Source: University of Illinois at Urbana-Champaign, News Bureau Summary: New evidence suggests that herbicide resistance in weeds is more likely to occur from pre-existing genetic variation than from new mutations.

After exposing more than 70 million grain amaranth seeds to a soil-based herbicide, researchers were not able to find a single herbicide-resistant mutant. Though preliminary, the findings suggest that the mutation rate in amaranth is very low, and that low-level herbicide application contributes little -- if anything -- to the onset of new mutations conferring resistance, researchers say.

The study is reported in the journal Weed Science.

Any major stress that does not kill a plant can contribute to genetic mutations in its seeds and pollen, said University of Illinois crop sciences professor Patrick Tranel, who led the new research. Even the ultraviolet light in sunlight can stress a plant and increase the likelihood of mutations in its offspring, he said. Such mutations increase genetic diversity, which can be useful to a species' survival.

"Resistance to herbicides comes from genetic variation in a population," Tranel said. "If an individual weed has the right mutation that allows it to survive a particular herbicide, that individual will survive and pass the trait to its progeny."

The relative contribution of new mutations to the problem of herbicide resistance is poorly understood, Tranel said. He and his colleagues hoped to determine the baseline mutation rate for a plant of the genus Amaranthus, a group that includes waterhemp, Palmer amaranth and other problematic agricultural weeds. They also wanted to test whether herbicide applications that failed to kill the plant increased that baseline rate.

The researchers started with a single seed of Amaranthus hypochondriacus, which is closely related to several agricultural weeds but is not known to harbor herbicide-resistance genes. Using a greenhouse to isolate their experiments from potential contamination from other Amaranthus species, the team cultivated this one plant, collected its seeds and began the long process of growing generations of related plants and harvesting the seeds.

"A good plant would produce about 100,000 seeds," Tranel said. "From this one plant, we eventually got more than 70 million seeds."

Despite the laboratory's isolation and the vigilance of the scientists, a few other Amaranthus weed seeds made their way into the experiment.

"These seeds are tiny and cling to things. You can have a seed stuck to your skin and not know it," Tranel said. "One of the students found a weed seed in his eyebrow after he left the greenhouse."

Luckily for the scientists, the seeds of the weedy Amaranthusspecies are black, while their test plants produced only light-colored seeds.

To screen the seeds for herbicide resistance, the researchers spread them over the surface of soil treated with a type of herbicide known as an ALS inhibitor, then waited to see whether any of the seedlings survived. Very few of the test plants overcame the herbicide treatment. Rigorous testing revealed that those rare plants that did survive were the offspring of seeds of weedy amaranth species that already carried the resistance genes.

The experiments verified that the scientists' approach worked well for screening vast numbers of seeds. It also established that the team would have to test many more than 70 million seeds to determine the baseline mutation rate in A. hypochondriacus -- and to figure out if low-level herbicide treatment increases that rate, Tranel said.

Knowing this is essential to developing models that can accurately predict how plants will behave in a field, he said.

"Herbicide resistance is an evolutionary process, and evolutionary processes are mathematical," Tranel said. "If you know more precisely how plants will behave under different environmental conditions, you can develop equations that will predict how fast resistance will evolve."

If, as the study suggests, the mutation rate is much lower than expected, it doesn't mean that herbicide resistance will not occur, he said. "It may be that resistance happens a bit more slowly than previously thought," he said. "But it will still occur."

Story Source:

Materials provided by University of Illinois at Urbana-Champaign, News Bureau. Note: Content may be edited for style and length.

Journal Reference:

Federico A. Casale, Darci A. Giacomini, Patrick J. Tranel. Empirical investigation of mutation rate for herbicide resistance. Weed Science, 2019; 1 DOI: 10.1017/wsc.2019.19

Cite This Page:

MLA

APA

Chicago

University of Illinois at Urbana-Champaign, News Bureau. "New mutations for herbicide resistance rarer than expected." ScienceDaily. ScienceDaily, 28 May 2019. <www.sciencedaily.com/releases/2019/05/190528140113.htm>.

Mathematics of plant leaves

Unusual Japanese plant inspires recalculation of equation used to model leaf arrangement patterns

Date: June 6, 2019 Source: University of Tokyo Summary: A Japanese plant species with a peculiar leaf pattern recently revealed unexpected insight into how almost all plants control their leaf arrangement.Share:

Leaves can be enjoyed for their shade, autumn colors, or taste, and the arrangement of leaves on a plant is a practical way to identify a species. However, the details of how plants control their leaf arrangement have remained a persistent mystery in botany. A Japanese plant species with a peculiar leaf pattern recently revealed unexpected insight into how almost all plants control their leaf arrangement.

"We developed the new model to explain one peculiar leaf arrangement pattern. But in fact, it more accurately reflects not only the nature of one specific plant, but the range of diversity of almost all leaf arrangement patterns observed in nature," said Associate Professor Munetaka Sugiyama from the University of Tokyo's Koishikawa Botanical Garden.

All in the angles

To identify the leaf arrangement of a plant species, botanists measure the angle between leaves, moving up the stem from oldest to youngest leaf.

Common patterns are symmetrical and have leaves arranged at regular intervals of 90 degrees (basil or mint), 180 degrees (stem grasses, like bamboo), or in Fibonacci golden angle spirals (like the needles on some spherical cacti, or the succulent spiral aloe).

The peculiar pattern that Sugiyama's research team studied is called "orixate" after the species Orixa japonica, a shrub native to Japan, China, and the Korean peninsula. O. Japonica is sometimes used as a hedge.

The angles between O. Japonica leaves are 180 degrees, 90 degrees, 180 degrees, 270 degrees, and then the next leaf resets the pattern to 180 degrees.

"Our research has the potential to truly understand beautiful patterns in nature," said Sugiyama.

The math of a plant

Sugiyama's research team began their investigation by doing exhaustive testing of the existing mathematical equation used to model leaf arrangement.

Leaf arrangement has been modeled mathematically since 1996 using an equation known as the DC2 (Douady and Couder 2). The equation can generate many, but not all, leaf arrangement patterns observed in nature by changing the value of different variables of plant physiology, such as the relationships between different plant organs or strength of chemical signals within the plant.

The DC2 has two shortcomings that researchers wanted to address:

No matter what values are put into the DC2 equation, certain uncommon leaf arrangement patterns are never calculated.

The Fibonacci spiral leaf arrangement pattern is by far the most common spiral pattern observed in nature, but is only modestly more common than other spiral patterns calculated by the DC2 equation.

A peculiar pattern

At least four unrelated plant species possess the unusual orixate leaf arrangement pattern. Researchers suspected that it must be possible to create the orixate pattern using the fundamental genetic and cellular machinery shared by all plants because the alternative possibility -- that the same, very unusual leaf arrangement pattern evolved four or more separate times -- seemed too unlikely.

One fundamental assumption used in the DC2 equation is that leaves emit a constant signal to inhibit the growth of other leaves nearby and that the signal gets weaker at longer distances. Researchers suspect that the signal is likely related to the plant hormone auxin, but the exact physiology remains unknown.

Rare patterns and common rules

"We changed this one fundamental assumption -- inhibitory power is not constant, but in fact changes with age. We tested both increasing and decreasing inhibitory power with greater age and saw that the peculiar orixate pattern was calculated when older leaves had a stronger inhibitory effect," said Sugiyama.

This insight into the inhibitory signal power changing with age may be used to direct future studies of the genetics or physiology of plant development.

Researchers call this new version of the equation the EDC2 (Expanded Douady and Couder 2).

First author of the research paper, doctoral student Takaaki Yonekura, designed computer simulations to generate thousands of leaf arrangement patterns calculated by EDC2 and to count how often the same patterns were generated. Patterns that are more commonly observed in nature were more frequently calculated by the EDC2, further supporting the accuracy of the ideas used to create the formula.

"There are other very unusual leaf arrangement patterns that are still not explained by our new formula. We are now trying to design a new concept that can explain all known patterns of leaf arrangement, not just almost all patterns," said Sugiyama.

Do it yourself -- ID the pattern

Experts recommend looking at a group of relatively new leaves when identifying a plant's leaf arrangement, or phyllotaxis, pattern. (In Greek, phyllon means leaf.) Older leaves may have turned (due to wind or sun exposure), which can make it difficult to identify their true angle of attachment to the stem.

Think of the stem as a circle and begin by carefully observing where on the circle the oldest and second-oldest leaves are attached. The angle between those two leaves is the first "angle of divergence." Continue identifying the angles of divergence between increasingly younger leaves on the stem. The pattern of angles of divergence is the leaf arrangement pattern.

Common leaf arrangement patterns are distichous (regular 180 degrees, bamboo), Fibonacci spiral (regular 137.5 degrees, the succulent Graptopetalum paraguayense), decussate (regular 90 degrees, the herb basil), and tricussate (regular 60 degrees, Nerium oleander sometimes known as dogbane).

Story Source:

Materials provided by University of Tokyo. Note: Content may be edited for style and length.

Related Multimedia:

Images of Orixa japonica and leaf arrangements

Journal Reference:

Takaaki Yonekura, Akitoshi Iwamoto, Hironori Fujita, Munetaka Sugiyama. Mathematical model studies of the comprehensive generation of major and minor phyllotactic patterns in plants with a predominant focus on orixate phyllotaxis. PLOS Computational Biology, 2019; 15 (6): e1007044 DOI: 10.1371/journal.pcbi.1007044

Cite This Page:

MLA

APA

Chicago

University of Tokyo. "Mathematics of plant leaves: Unusual Japanese plant inspires recalculation of equation used to model leaf arrangement patterns." ScienceDaily. ScienceDaily, 6 June 2019. <www.sciencedaily.com/releases/2019/06/190606150226.htm>.

How corn's ancient ancestor rejects crossbreeding

Date: May 24, 2019 Source: Carnegie Institution for Science Summary: New research elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.ry:New research elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.

Corn varieties (stock image).

Credit: © cpnjuansanchez / Adobe Stock

Determining how one species becomes distinct from another has been a subject of fascination dating back to Charles Darwin. New research led by Carnegie's Matthew Evans and published in Nature Communications elucidates the mechanism that keeps maize distinct from its ancient ancestor grass, teosinte.

Speciation requires isolation. Sometimes this isolation is facilitated by geography, such as mountains chains or islands that divide two populations and prevent them from interbreeding until they become different species. But in other instances, the barriers separating species are physiological factors that prevent them from successfully mating, or from producing viable offspring.

"In plants, this genetic isolation can be maintained by features that prevent the 'male' pollen of one species from successfully fertilizing the 'female' pistil of another species," explained Evans.

About 9,000 years ago, maize, or corn, was domesticated from teosinte in the Balsas River Valley of Mexico. Some populations of the two grasses are compatible for breeding. But others grow in the same areas and flower at the same time, but rarely produce hybrids.

It was known that a cluster of genes called Tcb1-s is one of three that confers incompatibility between these rarely hybridizing maize and teosinte populations. Unlike the other two, it is found almost exclusively in wild teosinte. It contains both male and female genes that encode wild teosinte's ability to reject maize pollen.

In sexually compatible plants, the pollen, which is basically a sperm delivery vehicle, lands on the pistil and forms a tube that elongates and burrows down into the ovary, where the egg is fertilized. But that's not what happens when maize pollen lands on the pistil, or silk, of a wild teosinte plant.

Evans and his colleagues -- Carnegie's Yongxian Lu (the first author), Samuel Hokin, and Thomas Hartwig, along with Jerry Kermicle of the University of Wisconsin Madison -- demonstrated that the Tcb1-female gene encodes a protein that is capable of modifying cell walls, likely making maize pollen tubes less elastic and thus preventing them from reaching the teosinte eggs. When these tubes can't stretch all the way to the eggs, fertilization can't occur, and hybrids won't be possible.

What's more, because teosinte pollen can fertilize itself, the researchers think that the Tcb1-male genes encode an ability that allows teosinte pollen to overcome this pollen tube barrier building.

"Most plants that depend on wind and water, not birds or insects, for pollination have low species diversity," said Evans. "But not grasses, which makes their evolutionary history particularly interesting."

This work was supported by the U.S. National Science Foundation and the U.S. Department of Agriculture National Research Initiative.

Story Source:

Materials provided by Carnegie Institution for Science. Note: Content may be edited for style and length.

Journal Reference:

Yongxian Lu, Samuel A. Hokin, Jerry L. Kermicle, Thomas Hartwig, Mathew M. S. Evans. A pistil-expressed pectin methylesterase confers cross-incompatibility between strains of Zea mays. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-10259-0

Cite This Page:

MLA

APA

Chicago

Carnegie Institution for Science. "How corn's ancient ancestor rejects crossbreeding." ScienceDaily. ScienceDaily, 24 May 2019. <www.sciencedaily.com/releases/2019/05/190524113517.htm>.

Goiás - Podostemaceae of Chapada dos Veadeiros National Park

https://fieldguides.fieldmuseum.org/sites/default/files/rapid-color-guides-pdfs/1003_brazil_podostemaceae_of_veadeiros_0.pdf

Santa Catarina - Climbing Plants of the Costa Brava Environmental Preservation Area

https://fieldguides.fieldmuseum.org/sites/default/files/rapid-color-guides-pdfs/1013_brazil_climbing_plants_apa_da_costa_brava.pdf

Santa Catarina - Orchidaceae of Costa das Orquídeas

https://fieldguides.fieldmuseum.org/sites/default/files/rapid-color-guides-pdfs/1011_brazil_orchidaceae_of_costa_das_orquideas.pdf

Bahia - Phanerogamic Flora of the Municipal Park of the Dunes: Most Common Species

https://fieldguides.fieldmuseum.org/sites/default/files/rapid-color-guides-pdfs/1017_brazil_phanerogamic_flora_of_the_municipal_park_of_the_dunes.pdf

Identificada planta que floresce no Cerrado apenas um dia depois de queimada

José Tadeu Arantes | Agência FAPESP – As plantas do Cerrado evoluíram na presença do fogo. E, quando usado com inteligência, como método de manejo criterioso, o fogo é fator indispensável para a preservação desse formidável ecossistema, que constitui a mais biodiversa savana do mundo. Bastam dois meses para que o Cerrado queimado se transforme em um jardim exuberante (leia mais em agencia.fapesp.br/25865 e agencia.fapesp.br/26325).

O estudo From ashes to flowers: a savanna sedge initiates flowers 24 hours after fire, publicado na revista Ecology nesta segunda-feira (25/03), confirmou essa teoria. O artigo enfocou uma espécie vegetal que inicia sua floração apenas 24 horas após a queima.

“Trata-se da Bulbostylis paradoxa, uma erva perene da família Cyperaceae, conhecida popularmente como cabelo-de-índio”, disse a primeira autora do artigo, Alessandra Fidelis, à Agência FAPESP.

Fidelis é professora da Universidade Estadual Paulista (Unesp), no campus de Rio Claro, e investigou o assunto com apoio da FAPESP no âmbito do projeto “Como a época do fogo afeta a vegetação do Cerrado”.

O Cerrado é uma savana peculiar. E sua capacidade de rebrotar e florescer depois de queimada é um importante diferencial em relação às savanas africanas e australianas. Isso já havia sido relatado, desde o século 19 e início do 20, por naturalistas que visitaram o Brasil, como o francês Auguste de Saint-Hilaire (1779-1853) e o dinamarquês Eugenius Warming (1841-1924). E, mais tarde, foi tema da tese de livre-docência do professor Leopoldo Magno Coutinho (1934-2016), da Universidade de São Paulo (USP). A própria Fidelis vem estudando essa regeneração pós-fogo do Cerrado desde 2009, mas o que chamou sua atenção, e constitui o ineditismo do artigo em pauta, é a rapidez com que a Bulbostylis paradoxa floresce. “É o único evento desse tipo descrito até o momento no mundo”, disse.

Bulbostylis paradoxa é uma planta amplamente difundida na América do Sul, desde a Venezuela até o sul do continente. E só floresce em escala significativa após o fogo. “Em nossos experimentos com queima criteriosa como prática de manejo, verificamos que as plantas dessa espécie, reduzidas pelo fogo à condição de tocos carbonizados, começam a apresentar pontinhos brancos 24 horas depois de queimadas. Esses pontinhos são as inflorescências despontando. Em pouco mais de uma semana, as flores se encontram completamente formadas e aptas à polinização. A rapidez da resposta constitui uma grande vantagem para a planta, porque possibilita que ela floresça, frutifique e disperse suas sementes por meio do vento em um espaço livre, com o solo descoberto, sem barreiras nem competidores. Apenas 40 dias depois do fogo já é muito difícil encontrar sementes, porque elas se disseminaram”, contou Fidelis.

De maneira geral, a grande oferta de sementes após a queima do Cerrado constitui um importante recurso para animais predadores, como formigas ou aves. A rebrota também oferece folhas mais tenras e palatáveis para mamíferos de grande porte, como veados e bois. O grande problema em relação ao fogo são os incêndios criminosos ou mesmo incêndios espontâneos que acabam assumindo proporções desastrosas devido ao acúmulo de material combustível depois de anos sem queima adequada.

“O Cerrado evoluiu com o fogo. Por isso, sua vegetação se regenera facilmente, inclusive com a manifestação de espécies que antes não ocorriam em determinadas áreas. A fauna, porém, pode sofrer perdas, pois muitos animais ficam presos nos incêndios. E, em relação à flora, é preciso lembrar que, no meio da vegetação do Cerrado, existem matas de galeria, matas de vale e veredas. Nesse caso, algumas espécies sensíveis ao fogo podem não se recuperar após os grandes incêndios. Por isso, é preciso haver um manejo criterioso do fogo. A queima preventiva, nas épocas certas, com zoneamento da área total e rodízio das parcelas a serem queimadas, constitui a melhor defesa contra os incêndios desastrosos”, explicou Fidelis.

A expansão da fronteira agrícola, com monoculturas em grande escala e uso intensivo de maquinário e herbicidas, que deixam o solo completamente limpo e sujeito à ação de plantas invasoras como braquiária e capim-gordura, constitui atualmente a maior ameaça à sobrevivência do Cerrado. A segunda principal ameaça é o uso inadequado do fogo. Conjugados, esses dois fatores põem em risco a manutenção de todo o ecossistema. Alguns dos mais importantes rios do Brasil nascem no Cerrado. Entre eles, o Xingu, o Tocantins, o Araguaia, o São Francisco, o Parnaíba, o Gurupi, o Jequitinhonha, o Paraná e o Paraguai. Além da irreparável perda de biodiversidade, a destruição do Cerrado compromete as bacias desses rios, com seu formidável aporte de água doce e potencial hidrelétrico.

Além de Fidelis, participaram do estudo Patrícia Rosalem, Vagner Zanzarini, Liliane Santos de Camargos e Aline Redondo Martins – todos da Unesp.

O artigo From ashes to flowers: a savanna sedge initiates flowers 24 hours after fire pode ser lido em: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2648.
 

Este texto foi originalmente publicado por Agência FAPESP de acordo com a licença Creative Commons CC-BY-NC-ND. Leia o original aqui.

Human history through tree rings: Trees in Amazonia reveal pre-colonial human disturbance

New study shows that tropical trees act as a living record of past human activity in the Amazon

Date: April 3, 2019 Source: Max Planck Institute for the Science of Human History

Summary:

The Brazil nut tree (Bertholletia excelsa) is well known around the world today and has been an important part of human subsistence strategies in the Amazon forest from at least the Early Holocene. These trees can live for hundreds of years and are managed today by humans for their valuable, energy-filled nuts. Patterns in the establishment and growth of living Brazil nut trees in Central Amazonia reflect over 400 years of changes in human occupation, politics, and socioeconomic activities in the region.

See more at:

https://www.sciencedaily.com/releases/2019/04/190403155443.htm

Ready, steady, go: Steps in plant immune receptor activation

Date: April 4, 2019 Source: Max Planck Institute for Plant Breeding Research Summary: Two landmark studies provide unprecedented structural insight into how plant immune receptors are primed -- and then activated -- to provide plants with resistance against microbial pathogens.

Although separated by more than one billion years of evolution, plants and animals have hit upon similar immune strategies to protect themselves against pathogens. One important mechanism is defined by cytoplasmic receptors called NLRs that, in plants, recognize so-called effectors, molecules that invading microorganisms secrete into the plant's cells. These recognition events can either involve direct recognition of effectors by NLRs or indirect recognition, in which the NLRs act as 'guards' that monitor additional host proteins or 'guardees' that are modified by effectors. Host recognition of effectors, whether direct or indirect, results in cell death to confine microbes to the site of infection. However, until now, a detailed understanding of the mechanisms of action of plant NLRs has been lacking, and much of our understanding of how these molecules function in plants has been based on comparison with animal counterparts.

In two new studies published in the journal Science, Jijie Chai who is affiliated with Tsinghua University in Beijing as well as the University of Cologne and the Max Planck Institute for Plant Breeding Research together with the groups of Hong-Wei Zhang and Jian-Min Zhou at Tsinghua University and the Chinese Academy of Sciences in Beijing have now pieced together the sequence of molecular events that convert inactive NLR molecules into active complexes that provide disease resistance.

The authors focused their attentions on a protein called ZAR1, an ancient plant molecule that is likely to be of broad importance since it interacts with multiple 'guardees' to recognize unrelated bacterial effectors.

Using cryo-electron microscopy, Chai and co-authors observed that in the absence of bacterial effectors, ZAR1, together with the plant protein RKS1, is maintained in a latent state through interactions involving multiple domains of the ZAR1 protein. Upon infection, a bacterial effector modifies the plant 'guardee' PBL2, which then activates RKS1 resulting in huge conformational changes that first allow plants to swap ADP for ATP and then result in the assembly of a pentameric, wheel-like structure that the authors term the 'ZAR1 resistosome'.

One striking feature of this structure is its similarity with animal NLR proteins, which, once activated, also assemble into wheel-like structures that act as signaling platforms for cell death execution and immune signaling. However, one important difference between the structures offers a tantalizing clue as to how ZAR1 induces cell death. The authors could identify a highly ordered funnel-like structure in ZAR1 that tethers the resistosome to the plasma membrane and is required for cell death and disease resistance. The authors speculate that ZAR1 may form a pore in the plasma membrane and in this way perturb cellular function leading to immune signaling and cell death.

Other plant NLRs also assemble into complexes that associate with the plasma membrane and it is thus highly likely that Chai's findings have important general implications for understanding plant immunity. MPIPZ director Paul Schulze-Lefert, who was not involved in the studies, is in no doubt about the importance of the new studies: "This will become textbook knowledge."

Story Source:

Materials provided by Max Planck Institute for Plant Breeding Research. Note: Content may be edited for style and length.

Journal References:

Jizong Wang, Jia Wang, Meijuan Hu, Shan Wu, Jinfeng Qi, Guoxun Wang, Zhifu Han, Yijun Qi, Ning Gao, Hong-Wei Wang, Jian-Min Zhou, Jijie Chai. Ligand-triggered allosteric ADP release primes a plant NLR complex. Science, 2019; 364 (6435): eaav5868 DOI: 10.1126/science.aav5868

Jizong Wang, Meijuan Hu, Jia Wang, Jinfeng Qi, Zhifu Han, Guoxun Wang, Yijun Qi, Hong-Wei Wang, Jian-Min Zhou, Jijie Chai. Reconstitution and structure of a plant NLR resistosome conferring immunity. Science, 2019; 364 (6435): eaav5870 DOI: 10.1126/science.aav5870

Cite This Page:

MLA

APA

Chicago

Max Planck Institute for Plant Breeding Research. "Ready, steady, go: Steps in plant immune receptor activation." ScienceDaily. ScienceDaily, 4 April 2019. <www.sciencedaily.com/releases/2019/04/190404143742.htm>.

How poppy flowers get those vibrant colors that entice insects

Date: February 8, 2019 Source: University of Groningen Summary: With bright reds and yellows -- and even the occasional white -- poppies are very bright and colorful. Their petals, however, are also very thin; they are made up of just three layers of cells. Scientists used microscopy and mathematical models describing how light interacts with petals to find out how the vibrant colors are created. 

Different poppies which were used in the study. 

Credit: University of Groningen 

With bright reds and yellows -- and even the occasional white -- poppies are very bright and colorful. Their petals, however, are also very thin; they are made up of just three layers of cells. University of Groningen scientists Casper van der Kooi and Doekele Stavenga used microscopy and mathematical models describing how light interacts with petals to find out how the vibrant colors are created. The results will be included in a special edition of the Journal of Comparative Physiology A, which focuses on the relationship between insects and flowers. 

Van der Kooi's main research focus is the evolution of flower color, and the interaction between flower color and pollinators. This led him to investigate how petals produce their visual signals. He explains why the flowers of poppies (Papaver, Meconopsis and related species) are interesting: 'The common poppy is an extreme case, it has very thin petals that nevertheless cause a very high scattering of light. Poppies also contain high concentrations of pigments.' 

Jigsaw pieces 

The researchers collected petals from different poppy species and studied their structures using different techniques. They discovered that the pigment was only present in the two outer cell layers and not in the middle layer. The pigmented cells had a fascinating shape, with many invaginations that made them look like complicated jigsaw pieces. 'This creates many air-filled gaps between the cells, which cause the reflection of light on the cell/air boundary', says Van der Kooi. 

Furthermore, the petals contained huge amounts of pigment. 'They are among the highest concentrations that I have ever measured in any flower.' Indeed, the characteristic black markings at the center of some poppy flowers are caused by extreme concentrations of red pigment. Van der Kooi concludes that dense pigmentation together with strong scattering causes the striking poppy colors in the red parts of the petal. 

Sexual mimicry 

The new findings can be linked to previous work on poppy color evolution. Intriguingly, poppies in the Middle East reflect no ultraviolet light, while the same species in Europe do. This difference may be due to their preferred pollinators. 'In Europe, poppies are pollinated mostly by bees, which cannot see red very well; however, they will pick up ultraviolet.' In contrast, poppies in the Middle East are pollinated by beetles that do see red colors. 

'Moreover, previous studies have shown that the black spots at the heart of some poppies mimic the presence of a female beetle. This is a way for the flowers to attract male beetles. A case of sexual mimicry, as occurs in other plants such as orchids', explains Van der Kooi. 

Air gaps 

The next question will be how these jigsaw-like cells and the air gaps that cause the efficient scattering have evolved. 'These cell shapes are commonly present in leaves, so that might be a clue.' Furthermore, results suggest that poppies evolved ultraviolet signals when they began growing in more northern regions. It makes the evolutionary history of these brightly colored flowers an interesting object of study. 

The paper by Van der Kooi and Stavenga will be included in a special edition of the Journal of Comparative Physiology A, edited by Friedrich Barth (University of Vienna). This special edition, with the title "Insects and Flowers. New insights into an old partnership," is due to appear in print late this spring. The paper has already been published online. 

Story Source: 

Materials provided by University of Groningen. Note: Content may be edited for style and length. 

Journal Reference: 

Casper J. van der Kooi, Doekele G. Stavenga. Vividly coloured poppy flowers due to dense pigmentation and strong scattering in thin petals. Journal of Comparative Physiology A, 2019; DOI: 10.1007/s00359-018-01313-1

Cite This Page: 

MLA

APA

Chicago

University of Groningen. "How poppy flowers get those vibrant colors that entice insects." ScienceDaily. ScienceDaily, 8 February 2019. <www.sciencedaily.com/releases/2019/02/190208115304.htm>.

How plants cope with stress

Date: October 30, 2018 Source: University of Pennsylvania Summary: With climate change comes drought, and with drought comes higher salt concentrations in the soil. Scientists have identified a mechanism by which plants respond to salt stress, a pathway that could be targeted to engineer more adaptable crops.

The future looks challenging for plants. Climate change is forecast to bring widespread drought to parts of the planet already struggling with dry conditions. To mitigate the potentially devastating effects to agriculture, researchers are seeking strategies to help plants withstand extreme environmental hazards including drought and salt stress, a problem exacerbated when irrigated water passes through the soil, depositing salts which can then absorbed by plant roots, lowering their overall productivity.

One tack is to look at ways that plants have naturally evolved to cope with stresses such as too much salt. In a new study out in Cell Reports, researchers led by University of Pennsylvania biologist Brian D. Gregory and graduate student Stephen J. Anderson have identified a mechanism that could potentially be manipulated to develop more salt-tolerant crops.

Their work shows that a tiny tag on RNA molecules -- the transcripts that are translated to produce proteins -- serves to stabilize and protect these strands of genetic material. When plants are exposed to high-salt conditions, the RNA mark, known as N6-methyladenosine, or m6A, prevents the breakdown of transcripts encoding proteins that help plants more effectively deal with the challenging conditions.

"This is how we're going to help farmers," says Gregory, an associate professor in Penn's Department of Biology in the School of Arts and Sciences and the senior author on the paper. "We need to identify ways that we can make more salt-resistant and drought-resistant plants, and manipulating this pathway might be one way to do it."

For an organism to produce any protein, it must first possess the corresponding strand of messenger RNA (mRNA). But not all mRNAs are turned into proteins; some are degraded before they reach that stage. In recent years, both mammalian and plant biologists have been paying attention to the m6A mark as a player in the process by which mRNAs are targeted to either keep around or destroy.

"There's been an explosion of interest in this mark," Gregory says. "It's been found to be the most abundant internal modification in mRNA."

In mammals, the bulk of research points to the mark labeling mRNA for destruction. And, while some studies have suggested it may function the same way in plants, Gregory, Anderson, and colleagues wanted to get a more global view.

Analyzing leaves from mature Arabidopsis, the researchers globally identified m6A in normal plants as well as in those in which the enzyme that adds m6A had been eliminated, thus experimentally depleting them of the mark.

They found that transcripts that were abundant when marked by m6A in the normal plants were much lower in the m6A-depleted mutant plants, a sign that the mark was acting in a protective capacity to stabilize the transcripts.

Closely comparing the normal and the mutant plants, the team found that m6A, when present, protected the transcripts by preventing an enzyme from degrading them. When this mark was missing, the transcripts were cleaved and subsequently degraded.

"It was kind of serendipitous," says Anderson, "but it turned out that this destabilization was occurring right next to where these marks should have been but weren't in the experimental group of plants."

The next step was to ask why the plants might have evolved this mechanism in the first place. The researchers had hints that m6A labeling might be involved in stress response, judging from the affected genes between the normal and mutant plants. But, to put it to the test, they grew plants in a high-salt soil and repeated their experiments.

The salt treatment, they discovered, caused plants to affix more m6A marks on mRNA transcripts associated with responding to salt stress, as well as drought stress. In other words, the plants were girding themselves to deal with an environmental challenge.

"This gives plants a dynamic and really powerful mechanism to regulate stress response," Gregory says. "You can move this mark onto transcripts you want to keep around."

"There's also evidence," Anderson says, "that plants may be able to actively remove the mark from transcripts they don't need. We're still investigating that mechanism."

"This work," says Karen Cone at the National Science Foundation, which funded the research, "provides exciting new understanding of how genomic information interacts with signals from the environment to produce beneficial outcomes for the organism. The results promise to open the door to future discoveries of how organisms use RNA-based mechanisms to maintain the robustness and adaptability they need to survive in the face of changing environments, a finding that is directly relevant to one of NSF's 10 Big Ideas, Understanding the Rules of Life: Predicting Phenotype."

In additional follow-up experiments, Gregory's lab will examine this mark's involvement in other stressful situations for plants, like when they are subject to damage from organisms like bacteria or fungi. Gregory and colleagues also plan to pursue experiments in plant species important to agriculture, such as soy beans.

Further study may also help them zero in on the mechanism by which plants attach this mark to transcripts, helping in the development of strategies for engineering plants that may better resist the challenging conditions posed by drought.

Story Source:

Materials provided by University of Pennsylvania. Note: Content may be edited for style and length.

Journal Reference:

Stephen J. Anderson, Marianne C. Kramer, Sager J. Gosai, Xiang Yu, Lee E. Vandivier, Andrew D.L. Nelson, Zachary D. Anderson, Mark A. Beilstein, Rupert G. Fray, Eric Lyons, Brian D. Gregory. N6-Methyladenosine Inhibits Local Ribonucleolytic Cleavage to Stabilize mRNAs in Arabidopsis. Cell Reports, 2018; 25 (5): 1146 DOI: 10.1016/j.celrep.2018.10.020

Cite This Page:

MLA

APA

Chicago

University of Pennsylvania. "How plants cope with stress." ScienceDaily. ScienceDaily, 30 October 2018. <www.sciencedaily.com/releases/2018/10/181030150659.htm>.

Plantas usam açúcar produzido na fotossíntese para saber a hora

Quantidade de açúcar indica nível de energia disponível para plantas aumentarem ou reduzirem ritmo de atividade

Por Júlio Bernardes - Editorias: Ciências Biológicas

24/08/2018

Ao perceber a quantidade de energia (açúcar) que possui, planta tem noção da passagem do tempo e pode organizar suas atividades ao longo do dia, antecipando-se à chegada do sol para fazer fotossíntese logo ao amanhecer, podendo crescer mais e melhor – Foto: Jucember/Wikimedia Commons

Uma pesquisa com a participação do Instituto de Química (IQ) da USP revela que as plantas usam o açúcar produzido na fotossíntese para regular seu relógio biológico. Os cientistas descobriram os caminhos utilizados pelas células vegetais para ajustar os horários de atividade das plantas (crescimento, metabolismo e armazenamento) à quantidade disponível de açúcar, ou seja, de energia. Assim, quando a disponibilidade é menor, a planta reduz seu ritmo de atividade. Os resultados contribuirão em estudos visando a aumentar a produtividade de cultivos como o da cana.

“O objetivo do trabalho é tentar entender como a percepção interna da quantidade de energia (açúcar) que a planta tem influencia a maneira como é percebida a passagem do tempo durante o dia”, diz o professor do IQ Carlos Hotta, que integrou o grupo de pesquisa. “Isso é importante porque é o modo das plantas se organizarem ao longo do dia, antecipando-se à chegada do Sol para poder fazer fotossíntese logo ao amanhecer. Plantas que usam o relógio biológico crescem mais e melhor.”

Professor Carlos Hotta: nível de açúcar indica situações de escassez energética – Foto: Cecília Bastos/USP Imagens

Na fotossíntese, as células das plantas capturam a luz solar, convertendo a energia do Sol em energia química e juntando gás carbônico e água para formar açúcares. “O estudo mostra que perceber o nível de açúcar é um modo da planta saber a quantidade de energia que possui, inclusive em situações de estresse, como casos de escassez”, aponta o professor. “Foi analisado como o relógio biológico da Arabidopsis thaliana, organismo modelo para estudos sobre plantas, responde à adição de açúcar”. A Arabidopsis é uma planta herbácea da família das Brassicaceae, a mesma do brócolis, da canola, da mostarda e do repolho.

Sinalização

A pesquisa descobriu que as plantas possuem moléculas que atuam como vias de sinalização, no caso a via do SnRK1, que mede o nível energético da planta, e se conecta a um fator de transcrição, o bZIP63. “O fator de transcrição é um tipo de proteína que funciona como ‘interruptor molecular’, atuando diretamente no DNA, ‘ligando’ e ‘desligando’ genes”, a partir das informações da via de sinalização, conta o pesquisador. “Há evidências de que um dos genes em que o bZIP63 atua é do relógio biológico, chamado de PRR7, o que faz com que a planta, conforme a energia disponível, altere os horários em que desempenha determinadas funções.”

Quando há menos energia, a via que sinaliza o estresse energético está mais ativa, mas quando o açúcar é abundante, ela permanece inativada, o que inibe o fator de transcrição. “Pesquisas anteriores sobre o relógio biológico avaliavam as plantas quando havia muita energia disponível, por isso a via não era percebida”, diz Hotta. “Quando começou-se a olhar para as plantas em condições de baixa energia, foi possível notar que essa via é essencial para a planta se reorganizar diante do estresse energético, mudar seu modo de vida e sobreviver”.

Amostras de Arabidopsis thaliana: via de sinalização que orienta o relógio biológico só foi percebida pelos cientistas quando a planta está em condições de baixa energia – Foto: Cecília Bastos/USP Imagens

Os resultados da pesquisa são descritos no artigo “Circadian Entrainment in Arabidopsis by the Sugar-Responsive Transcription Factor bZIP63”, publicado em 2 de agosto na revista científica Current Biology. “O estudo comprovou como os dois mecanismos moleculares impactam e regulam o funcionamento da planta”, ressalta o professor. “O próximo passo é investigar que funções são reguladas. Uma das hipóteses é de que possivelmente os mecanismos influenciem na forma que a planta armazena amido durante a noite.”

Produtividade

Hotta aponta que as descobertas do estudo poderão ser importantes em pesquisas sobre cultivos como o da cana-de-açúcar. “Saber que o açúcar é essencial para o relógio biológico muda a percepção sobre a sua função em plantas que acumulam muito açúcar, a cana, por exemplo”, observa. “Entender que o relógio biológico está associado à produtividade da planta ajuda a buscar formas de torná-la mais produtiva.”

A pesquisa foi realizada no Laboratório de Fisiologia Molecular de Plantas do IQ, em colaboração com os pesquisadores Michel Vincentz, da Universidade Estadual de Campinas (Unicamp), Alex Webb, da University of Cambridge, e Antony Dodd, da University of Bristol (Reino Unido). “Houve uma convergência dos estudos, facilitada pelas políticas de internacionalização da ciência adotadas no Brasil”, destaca o professor. “Na Unicamp, era pesquisada a influência do estresse energético no relógio biológico, enquanto os europeus estudavam as reações do relógio biológico ao estresse”. O trabalho teve apoio da Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp).

Mais informações: e-mail hotta@iq.usp.br, com Carlos Hotta

Link:
https://jornal.usp.br/ciencias/ciencias-biologicas/plantas-usam-acucar-produzido-na-fotossintese-para-saber-a-hora/

Carrot top pesto through the looking glass

Link:
https://botanistinthekitchen.blog/2017/09/23/carrot-top-pesto-through-the-looking-glass/
Posted on September 23, 2017 by Jeanne L. D. Osnas 

Isomers are molecules that have the same chemical constituents in different physical arrangements. Some terpenoid isomers have very different aromas and are important food seasonings. A batch of carrot top pesto led to an exploration of intriguing terpenoid isomers in the mint, carrot, and lemon families.

“Oh, c’mon. Try it,” my husband admonished me with a smile. “If anyone would be excited about doing something with them, I should think it would be you.”

The “them” in question were carrot tops, the prolific pile of lacy greens still attached to the carrots we bought at the farmer’s market. I have known for years that carrot tops are edible and have occasionally investigated recipes for them, but that was the extent of my efforts to turn them into food. My excuse is that I harbored niggling doubts that carrot tops would taste good. Edible does not, after all, imply delicious. My husband had thrown down the gauntlet, though, by challenging my integrity as a vegetable enthusiast. I took a long look at the beautiful foliage on the counter.

“Fine,” I responded, sounding, I am sure, resigned. “I’ll make a pesto with them.”

Carrot tops, it turns out, make a superb pesto. I have the passion of a convert about it, and not just because my carrot tops will forevermore meet a fate suitable to their bountiful vitality. The pesto I made combined botanical ingredients from two plant families whose flavors highlight the fascinating chemistry of structural and stereo isomers.

Continue reading →

Plants open their pores and scientists strike gold

Date: June 14, 2018 Source: Springer Summary: Plants containing the element gold are already widely known. The flowering perennial plant alfafa, for example, has been cultivated by scientists to contain pure gold in its plant tissue. Now researchers have identified and investigated the characteristics of gold nanoparticles in two plant species growing in their natural environments.

Plants containing the element gold are already widely known. The flowering perennial plant alfafa, for example, has been cultivated by scientists to contain pure gold in its plant tissue. Now researchers from the Sun Yat-sen University in China have identified and investigated the characteristics of gold nanoparticles in two plant species growing in their natural environments. The study, led by Xiaoen Luo, is published in Springer's journal Environmental Chemistry Letters and has implications for the way gold nanoparticles are produced and absorbed from the environment.

Xiaoen Luo and her colleagues investigated the perennial shrub B. nivea and the annual or biennial weed Erigeron Canadensis. The researchers collected and prepared samples of both plants so that they could be examined using the specialist analytical tool called field-emission transmission electron microscope (TEM).

Gold-bearing nanoparticles -- tiny gold particles fused with another element such as oxygen or copper -- were found in both types of plant. In E. Canadensis these particles were around 20-50 nm in diameter and had an irregular form. The gold-bearing particles in B. nivea were circular, elliptical or bone-rod shaped with smooth edges and were 5-15 nm.

"The abundance of gold in the crust is very low and there was no metal deposit in the sampling area so we speculate that the source of these gold nanoparticles is a nearby electroplating plant that uses gold in its operations, " explains Jianjin Cao who is a co-author of the study.

Most of the characteristics of the nanoparticles matched those of artificial particles rather than naturally occurring nanoparticles, which would support this theory. The researchers believe that the gold-bearing particles were absorbed through the pores of the plants directly, indicating that gold could be accumulated from the soil, water or air.

"Discovering gold-bearing nanoparticles in natural plant tissues is of great significance and allows new possibilities to clean up areas contaminated with nanoparticles, and also to enrich gold nanoparticles using plants," says Xiaoen Luo.

The researchers plan to further study the migration mechanism, storage locations and growth patterns of gold nanoparticles in plants and also verify the absorbing capacity of different plants for gold nanoparticles in polluted areas.

Story Source:

Materials provided by Springer. Note: Content may be edited for style and length.

Journal Reference:

Xiaoen Luo, Jianjin Cao. Discovery of nano-sized gold particles in natural plant tissues. Environmental Chemistry Letters, 2018; DOI: 10.1007/s10311-018-0749-0

Cite This Page:

MLA

APA

Chicago

Springer. "Plants open their pores and scientists strike gold." ScienceDaily. ScienceDaily, 14 June 2018. <www.sciencedaily.com/releases/2018/06/180614095226.htm>.

A rose is a rose is a rose: Mathematical model explains how two brains agree on smells

Researchers propose new and critical role for neurons in brain's smell center 

Date: May 1, 2018 Source: The Zuckerman Institute at Columbia University Summary: Scientists have discovered why the brain's olfactory system is so remarkably consistent between individuals, even though the wiring of brain cells in this region differs greatly from person to person. To make sense of this apparent paradox, the researchers developed a computational model showing that two brains need not have previously sniffed the same exact set of odors in order to agree on a new set of scents.

 

In a new study, Columbia scientists have discovered why the brain's olfactory system is so remarkably consistent between individuals, even though the wiring of brain cells in this region differs greatly from person to person. To make sense of this apparent paradox, the researchers developed a computational model showing that two brains need not have previously sniffed the same exact set of odors in order to agree on a new set of scents. Instead, any two brains will know to associate new similar odors with each other (such as two different flowers) so long as both brains have experienced even the smallest overlap in odors during their lifetimes.

This work was published last week in Neuron.

"Many of the brain cells, or neurons, in our olfactory system are wired together seemingly at random, meaning that the neurons that activate when I smell a rose are different than yours. So why do we both agree with certainty what we're smelling?" said the paper's senior author Larry Abbott, PhD, a computational neuroscientist and principal investigator at Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute. "By creating this model, we could detect, for the first time, the patterns that underlie seemingly random activity, revealing a mathematical consistency to how our brains are identifying scents."

The journey an odor takes from the nose to the brain is labyrinthine. When an odor enters the nasal cavity, specialized proteins called olfactory receptors send information about that scent to a designated location in the brain called the olfactory bulb. In a series of pioneering studies in the 1990s, Richard Axel, MD, a codirector at Columbia's Zuckerman Institute and a co-author of the new Neuron paper, discovered the more than 1,000 genes that encode these olfactory receptors. This work, which was performed alongside his colleague Linda B. Buck, PhD, earned them both the 2004 Nobel Prize in Physiology or Medicine.

Today's paper focuses on how information leaves the olfactory bulb and is interpreted by a brain region called the piriform cortex. The piriform cortex is believed to be a crucial structure for processing odors. Because no two whiffs of an odor are identical, the brain must make associations between odors that are similar. This process, called generalization, is what helps the brain to interpret similar smells.

"Generalization is critical because it lets you take the memory of a previous scent -- such as coffee -- and connect it to the odor of coffee you're currently smelling, to guide you as you stumble to the kitchen in the morning," said Evan Schaffer, PhD, a postdoctoral researcher in the Axel lab and the paper's first author.

However, as scientists have investigated the concept of generalization, they have been puzzled by two paradoxes about the piriform cortex. First, the neural activity in the piriform cortex appeared random, with no apparent logic or organization, so researchers could not tie a particular pattern of neural activity to a class of scents.

And second, the piriform cortex itself seemed too big. "Scientists could deduce a need for only about 50,000 of the roughly one-million piriform cortex neurons in the human brain," said Dr. Schaffer. "Given how energetically expensive neurons are, this raised the question: Why are there so many neurons in this part of the brain?"

The researchers developed a mathematical model that offered a resolution to both paradoxes: Two brains could indeed agree on a class of scents (i.e. fragrant flowers versus smelly garbage) if the neural activity came from a large enough pool of neurons.

The idea is similar to crowdsourcing, whereby different people each analyze one part of a complex question. That analysis is then pooled together into a central hub.

"This is analogous to what is happening in the piriform cortex," said Dr. Schaffer. "The different patterns of neural activity generated by these one-million neurons, while incomplete on their own, when combined give a complete picture of what the brain is smelling."

By then testing this model on data gathered from the brains of fruit flies, the team further showed that this neural activity helps two brains to agree on common odors, even with limited common experience.

Scientists have long argued that two brains must share a common reference point, such as each having previously smelled a rose, in order to identify the same scent. But this model suggests that the reference point can be anything -- the memory of the scent of a rose can help two people agree on the smell of coffee.

"Even the tiniest bit of common experience seems to realign the brains, so that while my neural activity is different than yours, the association we each make between two related scents -- such as flowers -- is similar for both of us," said Dr. Schaffer.

This model, while lending insight into a long-held paradox of perception, highlights an underlying elegance to the olfactory system: despite containing different neurons, memories and experiences -- two brains can still come to an agreement.

"You and I don't need to have sniffed every type of odor in the world to come to an agreement about what we're smelling," said Dr. Schaffer. "As long we have a little bit of common experience, that's enough."

Story Source:

Materials provided by The Zuckerman Institute at Columbia University. Note: Content may be edited for style and length.

Journal Reference:

Evan S. Schaffer, Dan D. Stettler, Daniel Kato, Gloria B. Choi, Richard Axel, L.F. Abbott. Odor Perception on the Two Sides of the Brain: Consistency Despite Randomness. Neuron, 2018; DOI: 10.1016/j.neuron.2018.04.004

Cite This Page:

MLA

APA

Chicago

The Zuckerman Institute at Columbia University. "A rose is a rose is a rose: Mathematical model explains how two brains agree on smells: Researchers propose new and critical role for neurons in brain's smell center." ScienceDaily. ScienceDaily, 1 May 2018. <www.sciencedaily.com/releases/2018/05/180501130800.htm>.